Simulated images are used in various applications, such as training simulators, electronic games, and visual planning and modeling tools. Using realistic simulated images in such applications is desirable to visually present and represent real world scenarios as it may be seen by the human eye outside of the application. In particular, it would be desirable to realistically simulate an outside scene including terrain and sky and the naturally occurring effects of atmospheric light on the scene. Although some simulation applications, such as games, provide a believable representation of outside scenes, these applications do not represent natural atmospheric lighting phenomena in a visual or photo realistic manner. For example, it would be desirable in a military training simulator to present training scenarios that realistically simulate an outside natural scene, including terrain, sky and lighting effects. Simulations using realistic outside scenes will make the image synthesis process more intuitive and have a broader scope of applications.
However, the realistic simulation of outdoor scenes presents significant challenges because of the geometry and lighting effects naturally occurring in such environments. The shapes of natural objects found in outdoor scenes and the effect of light and illumination on these natural objects make it particularly challenging to realistically simulate. Outdoor scenes exhibit great geometric complexity, and the sheer scale of outdoor scenes is typically significantly larger than that of indoor scenes. Furthermore, outdoor scenes often contain natural objects that have complex shapes. The geometric representation of the physical features of varying land mass, sky line and other terrain and atmospheric objects can be quite complex. Another challenge with outdoor scenes is the complexity of the illumination itself. The sky essentially surrounds all objects in the outside scene. Natural illumination from the sun and the sky has special and naturally occurring reflective and optical properties. As such, the lighting effects from the natural illumination affect the color and brightness of objects, terrain and atmosphere in the outside scene.
The realistic and efficient simulation of outdoor scenes is even further challenging. In order to create realistic simulations of outdoor scenes, such as a photo realistic simulation of a terrain and sky, simulating and rendering the visual effects from natural atmospheric lighting phenomena is required. The simulation needs to take into account the interaction of atmospheric light with the natural and man-made objects in the outside scene and the dynamics of natural systems. However, the modeling of such natural atmospheric lighting phenomena is difficult. Although accurate mathematical models of atmospheric lighting phenomena exist, the execution of such models in a simulation environment is very time consuming with a heaving computational burden. Moreover, because outdoor scenes are geometrically complex, the execution of accurate models for atmospheric lighting phenomena integrated with the geometric complexity of the scene is even more time consuming. As such, these models are not executed in real-time.
Thus it is desired to realistically simulate and render in real-time natural atmospheric lighting phenomena in outdoor scenes. Systems and methods are needed to realistically simulate and render in real-time the complexity of natural objects in outdoor scenes integrated with the visual effects from atmospheric lighting phenomena.